Oxidation of hydrocarbons



Feb. 26, 1935.

E. w. HULTMAN OXIDATION 0F HYDROCARBONS originai Filed Aprii so; 19:50

Patented Feb. '26, 1935 UNlTED STATES PATENT OFFICE K OXIDATION 0FHYDBOCABBONS Edgar W. lultman, Los Angeles, Calif., assigner to Hultmanand Powell Corp., corporation of Delaware never, nel., a

Application April 3o, 1930, serai No. 448,801

Renewed October 26, 1934 12 claims.

' oxidation compounds. 'Ihe oxidation compounds of the hydrocarbons aregenerally soluble, to a considerable extent at least, in the electrolyteand can be separated therefrom by a suitable method, for examplefractional distillation, after which the electrolyte, after suitabledilution if deslired, can again be oxidized in the electrolytic ce l Ina copending application 390,657 filed September 5, 1929, I havedescribed a process of reining petroleum products including gasoline andvarious others. by treating with an electrolytically oxidized refiningagent consisting for example of dilute sulphur-ic acid of 35 to 80 percent, and preferably around 50 per cent strength.

In the present process I also use such an electro-v lyte which isoxidized electrolytically, and contacted with the liquid oil orpetroleum distillate, the contacting preferably being effected veryshortly after the formation of the oxidized sulphuric acid.

The oxidation of the sulphuric acid may be lperformed by passing adirect current of electricity through sulphuric acid of say 50 per cent,

.although the strength may vary between about 30 per cent and about 80per cent, the object of the electrolysis being to form considerablequantities of oxidation products of sulphuric acid, such as persulphuricacid, Caros acid, and hydrogen peroxide. Ozone or oxygen may also beproduced to a considerable extent.

The oxidation of the electrolyte may conveniently be performed in a cellhaving a platinum anode, and a lead cathode, separated by a suitableceramic diaphragm, thelatter may be in the shape of an inverted bowl,and the platinum anode may be water-cooled, for example it may consistof a coil of platinum tubing lthrough which cooling water is causedf toflow. The cathy ode may be a strip of lead or a lead cup, in the outercompartment of the cell surrounding the -bowl above referred to.

From the anode compartment, which thus may consist of the inverted bowla smallopen tube leads upwardly into a superposed receptacle containingthe hydrocarbon liquid to be treated.

The oxidized electrolyte from the anode 'compartment ofthe electrolyticcell passes up through this tube bubbling into the hydrocarbon, and atonce reacts vigorously therewith giving the hydrocarbon theappearance'of boiling', and bubblesof gas being formed and escaping fromthe said oil. The alcohol produced in the oil by such oxidation, as wellas the aldehydes andfatty acids mostly dissolve in the acid electrolyteand the exhausted electrolyte carrying the organic oxidation products insolution, settles to the bottom of the oil receptable, being drawn of!again 'into the outer compartment of the electrolytic cell. 'I'hisoperation is continued until itis found that a desired amount ofoxidation has been performed, when the electrolyte may contain say 5 to10% of dissolved oxidation products oi the oil, and the, electrolyte canthen be passed to a still and the alco-` hol, aldehyde and fatty acidsdistilled off, during which operation of course a good deall of thewater content of the electrolyte would also distill on, and thesulphuric acid can then be diluted to about 50 per cent and cooled andagainintroduced into the electrolytic cell. If desired a portion oftheelectrolyte can be continuously drawn off, distilled to recover theoxidation products of the hydrocarbon, diluted, cooled and againcontinuously reintroduced into the electrolytic cell. 'I'his mode ofseparation is given by way or example, and any suitable mode ofseparation can be employed.

The processcan be continued until as much as half of the body ofhydrocarbon has been converted into oxidation products. v

The temperature of the liquid in the electrolytic cell is preferablykept down, for example by the cooling water in the tubular anode or inany other suitable manner, preferably to as low as 60 F., or lower. Thelower the temperature of the eleotrolyte the morel stable is thepersulphuric acid land other oxidation products of the electrolyte.

The hydrocarbon liqui'd inv the treating receptacle should b'e kept coolenough to prevent excessive amounts of vaporization of the same, thismaterial may bey at about ordinary room tempossible to produce alcoholscontaining more than two OH groups.

Without restricting the invention to details, it is stated that thevoltage may be at about 7 to 17, at 5 to 15 amperes. In a particularcase 18 volts at 10 amperes gave very satisfactory results. y

This corresponded .to about amperes per ,square decimeter of anode area,and the ratio of cathode surface to anode surface was about 15:1.Without restricting the invention to details, the following examples ofthe process are given.

Example 1 A straight run (uncracked) petroleum ether boiling between 40and '70 C. constituted the starting material. This consisted largely ofpentane, hexane and heptane, and was substantially free from unsaturatedhydrocarbons and was also substantially free from sulphur. The liquidwas .put into the flask above described, which was positioned over theelectrolytic cell with two glass tubes passing through the bottom of theflask forming the two passageways above referred to. The current waspassed between the electrodes, in this case a current from a 10 voltline, at about 8 amperes was employed. The acid from theanodiccompartment passed up through the vertical tube into contact with thepetroleum ether, and the bubbles and flow produced gave the latter theappearance of boiling. The dilute acid'separated out from thehydrocarbon in the bottom of the. flask, and was allowed to run backinto the outer compartment (cathode compartment) of the electrolyticcell, adjustment being had by a suitable valve in the said uoutlet tube.The temperature in the electrolytic cell was maintained between and 62F., and the temperature of the petroleum ether was about 'l0 to '72 F.Alfter being allowed to run for 3 to 5 minutes the electrolyte was foundVto contain a considerable amount of alcohols, including butyl, amyl,hexyl and heptyl. After running for 10 to 15 minutes', the correspondingaldehydes were found to be present lin the electrolyte to a considerableextent, and after running for fhalf anhour it was found that thecorresponding fatty acids were present in the electrolyte, theconcentration of the same being about 5%.

The solution of the electrolyte was run through a still, and the organiccompounds above referred to were separated from the same bydistillation. The residual acid was then diluted to 50% and cooled andbrought back into the electrolytic cell,

l for regeneration of the oxidizing agent.

Example 2 A cracked petroleum ether, that is to say a petroleum ether orliquid having a boiling point range of from about 40 to about '10 C.,made by cracking a heavier petroleum product, was used as the startingmaterial. The procedure was carried on as in the above example, and itwas Y found that a large percentage of dihydric alco- Example 3 IGasoline was first treated in accordance with the example of the priorapplication 390,657 above referred to, for the removal of sulphur. Thesulphur was largely removed from the gasoline during the first fourminutes of treatment. The treatment was then continued giving resultssimilar to the above, but higher alcohols being largely produced. Insome cases considerable amounts of butyric acid, together with some ofthe higher acids were also produced.

In some eases cracked gasoline high in oleflnes and other unsaturatedcompounds are found to give considerable amounts of higher glycols.

It will be understood that the process can be accelerated to some extentby the use of suitable catalytic agents, thus for example ceriumsulphate can be used as a constituent of the electrolyte, along with thesulphuric acid as above described,

My tests have indicated that up to 40 or 50%,

-more or less, of the petroleum ether can be converted into the oxidizedbodies, by continuing the running.

While I have referred particularly to low boiling oils, such aspetroleum ether and gasoline, I call attention to the fact that theinvention embraces the treatment of oils of any degree of volatility orboiling point range, such as kerosenes, motor oils, and heavier oils,and is not restricted to the lighter distillates. The invention isequally applicable whether or not the oils contain sulphur compounds orother impurities.

A highly important feature of the present invention resides in bringingthe oxidized electrolyte very promptly after its formation into contactwith the oil. An electrolyte which has been allowed to stand, even for afew minutes isnot nearly as effective. A mixture containing sulphuricacid and persulphuric acid, made for example by adding potassiumpersulphate to a largeexcess of 50% sulphuric acid is not very effective(if useful at all) for producing the results of the present process.

The process can be carried out in apparatus such as is illustrateddiagrammatically in the annexed drawing, forming a part of thisapplication. Y

A receptacle 10, which may be in the form of a large earthenware jar isprovided, and this contains a plate 11 which also canv be made ofearthenware, thereby forming an upper and a lower compartment. The lowercompartment can be filled with sulphuric acidof the concentrationreferred to above. The anode may be a platinum wire or platinum foilindicated at 12, this being positioned within a glass bowl or cup 13,which has a spout projecting upwardly through a hole in the central partof the plate 11, as indicated at 14. The cathode may be a cylindricallead cup, open at the top and bottom, as indicated at 15. Within thelower compartment, and preferably located in and around the anode cup 13is a refrigerating coil 16, for maintaining the liquid in and near thecathode compartment at a low temperature, for example at 60 C. or lower.

The-receptacle 10 is first illled with electrolyte up `to about thelevel 17, after which the apparatus is filled with the hydrocarbon oilto be treated, say up to the level 18. A direct current is then passedin from the lead 19 to the anode 12, the cathode l5 being connected tothe lead 20. When the current of electricity is passed, hxdrogen s givenoli' at the cathode, which nds its exit through the pipe 21, and can besuitably utilized. Water or very dilute sulphuric a'cid is added fromtime to time, through the pipe 22, for maintaining the acid level at 17,and a portion of the electrolyte. will ilow upwardly through the passage14, and will cause considerable stirring in the oil,

oxidizing the oil as indicated above, the spent .f will thereby assistthe ilow of the electrolyte from the compartment 13 into the oil,whereby the said electrolyte is brought into contact with the oil verysoon after formation ci' the electrolyte, and without allowing suchdecomposition of the electrolyte as would take place on standing for aprotracted period.

I claimtf 1. A process of producing exidation products from hydrocarbonswhich comprises oxidizing .sulphuric acid by electrolytic oxidation toiorm a carbons, such bringing together of said materials being effectedpromptly after the production oi said oxidation products, 4andcontinuing the treatment until the aqueous acid liquid contains thedesired products of oxidation of said hyrocarbons, in a substantialamount.

3. A process which comprises circulating a dilute sulphuric acidelectrolyte containing about 30 to 80% of H2804, through an electrolyticcell and bringing the anodic oxidation product at once into contact witha petroleum hydrocarbon, and continuing such treatment until saidelectrolyte has accumulated a substantial amount of oxidation productsof said hydrocarbon, separating the oxidation products -oi thehydrocarbon from the sulphuric acid and reintroducing the latter, asdilute acid, into said cycle. 4. A process which comprises circulating adilute sulphuric acid electrolyte through an electrolytic cell andbringing the anodic oxidation products at once into contact with apetroleum hydrocarbon not substantially more volatile than gasoline, andcontinuing such treatment until said electrolyte has accumulated asubstantial amount of oxidation products of said hydrocarbon, separatingthe oxidation products of the hydrocarbon from the sulphuric acid andreintroducing the latter, as dilute acid into said cycle.

5. A process which comprises circulating a dilute sulphuric acidelectrolyte through an electrolytic cell and then at once into contactwith a hydrocarbon consistingy largely of petroleum ether, andcontinuing such treatment until san` electrolyte has accumulated asubstantial amount of oxidation products of said hydrocarbon, separatingthe oxidation products of the hydrocarbon from the sulphuric acid andreintroducing the latter, as dilute acid into said cycle.

6. A process which comprises circulating a dilute sulphuric acid ofabout 30 to 80% strength, Ipreferably around 50% strength through anelectrolytic cell and bringing the anodlc oxidation products at onceinto contact with an open chain hydrocarbon, and continuing suchtreatment until said electrolyte has accumulated a substantial amount ofoxidation products of said hydrocarbon, separating the oxidationproducts of the hydrocarbon iromthe sulphuric acid and reintroduclng thelatter, as dilute acid into the saidl 1 cycle.

'7. A process of electrolytically oxidizing yan electrolyte containingdilute sulphuric acid in an electrolytic cell, surmounted by a treatingreceptacle at'only a short distance therefrom, passing the oxidationproduct of such electrolysis upward directly into said treatingreceptacle into contact with a low-boiling petroleum fraction, wherebythe latter becomes oxidized and taken up to some lextent at least by theacid, and thereafter re' continuing such treatment until saidelectrolytev has accumulated a substantial amount 'of oxidation productsof said hydrocarbon, separating the oxidation products of thehydrocarbon from the sulphuric acid and reintroducing the latter, as

ldilute acid into said cycle.

9. A process which comprises circulating a dilute sulphuric acidelectrolyte through an elec trolytic cell under conditions capable ofoxidizing the same and into contact with a petroleum fraction lessvolatile than kerosene, and continuing such treatment until saidelectrolyte has accumulated a substantial amount of oxidation productsof said hydrocarbon, separating the oxidation products of thehydrocarbon from the sulphuric lacid and reintroducing the latter, asdilute acid into said cycle.

i 10. A process which comprises circulating a dilute sulphuric acidelectrolyte through an electrolyticl cell capable of oxidizing such acidand then in contact with a hydrocarbon consisting largely oi petroleumether, and continuing such treatment until said electrolyte has`accumulated a substantial amount of oxidation products oi saidhydrocarbon, separating the oxidation products ,oi the hydrocarbon fromthe sulphuric acid by distillation and reintroducing the latter, asdilute acid into said cycle.

11. A process which comprises circulating a lute sulphuric acidelectrolyte containing about 30 to 80% of H2SO4, through an electrolyticcell and bringing the anodic oxidation product at once into contact witha petroleum hydrocarbon, and 5 continuing such treatment until saidelectrolyte has accumulated a substantial amount of oxidation productsof said hydrocarbon containing at least one of the herein describedgroup consist,-

ng of alcohol, aldehyde and fatty acid, s'aparat- 1 ing such oxidationproducts of hydrocarbon from the sulphuric acid and rentroducns;r thelatter, as dilute acid, into said cycle.

EDGAR W. HULTMAN.

